The continuous drive to print smaller structures for advanced electronic device manufacturing requires the use of higher resolution optical lithography tools. Immersion lithography has the potential to extend current 193 nm technology to 45 nm critical dimensions and beyond by enabling lens designs with NA greater than 1.0, thus resulting in an increased resolution of optical scanning exposure tools. In addition, immersion lithography effectively improves the depth-of-focus processing window. Immersion lithography requires filling the gap between the last lens element of the exposure tool and the photoresist-coated substrate with an immersion fluid such as water.
One of the technical challenges facing liquid immersion lithography is the possibility of inter-diffusion between the photoresist components and the immersion medium. That is, during the immersion lithographic process, the photoresist components can leach into the immersion medium and the immersion medium can permeate into the photoresist layer. Such extraction of photoresist components is detrimental to photoresist performance and might result in lens damage or contamination of expensive lithography tools. Therefore, there is a need for materials and methods to prevent or reduce interaction between photoresist layers and immersion fluid in an immersion lithography system.